Megakaryocyte Cytoskeletal Proteins in Platelet Biogenesis and Diseases

AbstractThrombopoiesis governs the formation of blood platelets in bone marrow by converting megakaryocytes into long, branched proplatelets on which individual platelets are assembled. The megakaryocyte cytoskeleton responds to multiple microenvironmental cues, including chemical and mechanical stimuli, sustaining the platelet shedding. During the megakaryocyte's life cycle, cytoskeletal networks organize cell shape and content, connect them physically and biochemically to the bone marrow vascular niche, and enable the release of platelets into the bloodstream. While the basic building blocks of the cytoskeleton have been studied extensively, new sets of cytoskeleton regulators have emerged as critical components of the dynamic protein network that supports platelet production. Understanding how the interaction of individual molecules of the cytoskeleton governs megakaryocyte behavior is essential to improve knowledge of platelet biogenesis and develop new therapeutic strategies for inherited thrombocytopenias caused by alterations in the cytoskeletal genes.

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Modulated polarization microscopy displays the dynamics of cytoskeletal structures in living, motile cells

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100140889 ◽

1995 ◽

Vol 53 ◽

pp. 902-903

Author(s):

J. R. Kuhn ◽

M. Poenie

Keyword(s):

Mitotic Spindle ◽

Actin Filaments ◽

Cell Shape ◽

Dynamic Structure ◽

Living Cells ◽

Cytoskeletal Proteins ◽

Polarization Microscopy ◽

Video Enhancement ◽

Ultrastructural Studies ◽

Motile Cells

Cell shape and movement are controlled by elements of the cytoskeleton including actin filaments an microtubules. Unfortunately, it is difficult to visualize the cytoskeleton in living cells and hence follow it dynamics. Immunofluorescence and ultrastructural studies of fixed cells while providing clear images of the cytoskeleton, give only a static picture of this dynamic structure. Microinjection of fluorescently Is beled cytoskeletal proteins has proved useful as a way to follow some cytoskeletal events, but long terry studies are generally limited by the bleaching of fluorophores and presence of unassembled monomers.Polarization microscopy has the potential for visualizing the cytoskeleton. Although at present, it ha mainly been used for visualizing the mitotic spindle. Polarization microscopy is attractive in that it pro vides a way to selectively image structures such as cytoskeletal filaments that are birefringent. By combing ing standard polarization microscopy with video enhancement techniques it has been possible to image single filaments. In this case, however, filament intensity depends on the orientation of the polarizer and analyzer with respect to the specimen.

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Revealing the Roles of Keratin 8/18-Associated Signaling Proteins Involved in the Development of Hepatocellular Carcinoma

International Journal of Molecular Sciences ◽

10.3390/ijms22126401 ◽

2021 ◽

Vol 22 (12) ◽

pp. 6401

Author(s):

Younglan Lim ◽

Nam-On Ku

Keyword(s):

Hepatocellular Carcinoma ◽

Transcription Factors ◽

Liver Damage ◽

Cell Shape ◽

Mutation Frequency ◽

Cytoskeletal Proteins ◽

Signaling Proteins ◽

Intermediate Filament Proteins ◽

Keratin 8 ◽

Keratin 18

Although hepatocellular carcinoma (HCC) is developed with various etiologies, protection of hepatocytes seems basically essential to prevent the incidence of HCC. Keratin 8 and keratin 18 (K8/K18) are cytoskeletal intermediate filament proteins that are expressed in hepatocytes. They maintain the cell shape and protect cells under stress conditions. Their protective roles in liver damage have been described in studies of mouse models, and K8/K18 mutation frequency in liver patients. Interestingly, K8/K18 bind to signaling proteins such as transcription factors and protein kinases involved in HCC development. Since K8/K18 are abundant cytoskeletal proteins, K8/K18 binding with the signaling factors can alter the availability of the factors. Herein, we discuss the potential roles of K8/K18 in HCC development.

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Pleiotrophin Regulates the Retention and Self-Renewal of Hematopoietic Stem Cells in the Bone Marrow Vascular Niche

Cell Reports ◽

10.1016/j.celrep.2012.09.002 ◽

2012 ◽

Vol 2 (4) ◽

pp. 964-975 ◽

Cited By ~ 80

Author(s):

Heather A. Himburg ◽

Jeffrey R. Harris ◽

Takahiro Ito ◽

Pamela Daher ◽

J. Lauren Russell ◽

...

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Hematopoietic Stem Cells ◽

Self Renewal ◽

Hematopoietic Stem ◽

Vascular Niche ◽

Bone Marrow Vascular Niche

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Platelet microparticles are released from blood platelets and bone marrow cells and stimulate endothelial invasion and neovascularisation

Vascular Pharmacology ◽

10.1016/j.vph.2006.08.322 ◽

2006 ◽

Vol 45 (3) ◽

pp. e120-e121

Author(s):

Lukasz Partyka ◽

Joanna Grzybowska ◽

Urszula Czech ◽

Anna Polus ◽

Lukasz Wator ◽

...

Keyword(s):

Bone Marrow ◽

Bone Marrow Cells ◽

Blood Platelets ◽

Platelet Microparticles ◽

Marrow Cells

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Localization and Interactions of Teichoic Acid Synthetic Enzymes in Bacillus subtilis

Journal of Bacteriology ◽

10.1128/jb.01394-07 ◽

2007 ◽

Vol 190 (5) ◽

pp. 1812-1821 ◽

Cited By ~ 63

Author(s):

Alex Formstone ◽

Rut Carballido-López ◽

Philippe Noirot ◽

Jeffery Errington ◽

Dirk-Jan Scheffers

Keyword(s):

Bacillus Subtilis ◽

Cell Shape ◽

Spatial Organization ◽

Structural Integrity ◽

Fluorescent Protein ◽

Teichoic Acid ◽

Cytoskeletal Proteins ◽

Thick Wall ◽

Wall Teichoic Acid ◽

Critical Function

ABSTRACT The thick wall of gram-positive bacteria is a polymer meshwork composed predominantly of peptidoglycan (PG) and teichoic acids, both of which have a critical function in maintenance of the structural integrity and the shape of the cell. In Bacillus subtilis 168 the major teichoic acid is covalently coupled to PG and is known as wall teichoic acid (WTA). Recently, PG insertion/degradation over the lateral wall has been shown to occur in a helical pattern. However, the spatial organization of WTA assembly and its relationship with cell shape and PG assembly are largely unknown. We have characterized the localization of green fluorescent protein fusions to proteins involved in several steps of WTA synthesis in B. subtilis: TagB, -F, -G, -H, and -O. All of these localized similarly to the inner side of the cytoplasmic membrane, in a pattern strikingly similar to that displayed by probes of nascent PG. Helix-like localization patterns are often attributable to the morphogenic cytoskeletal proteins of the MreB family. However, localization of the Tag proteins did not appear to be substantially affected by single disruption of any of the three MreB homologues of B. subtilis. Bacterial and yeast two-hybrid experiments revealed a complex network of interactions involving TagA, -B, -E, -F, -G, -H, and -O and the cell shape determinants MreC and MreD (encoded by the mreBCD operon and presumably involved in the spatial organization of PG synthesis). Taken together, our results suggest that, in B. subtilis at least, the synthesis and export of WTA precursors are mediated by a large multienzyme complex that may be associated with the PG-synthesizing machinery.

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The Dynamic Interface Between the Bone Marrow Vascular Niche and Hematopoietic Stem Cells in Myeloid Malignancy

Frontiers in Cell and Developmental Biology ◽

10.3389/fcell.2021.635189 ◽

2021 ◽

Vol 9 ◽

Author(s):

Laura Mosteo ◽

Joanna Storer ◽

Kiran Batta ◽

Emma J. Searle ◽

Delfim Duarte ◽

...

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Hematopoietic Stem Cells ◽

Hematopoietic Stem ◽

Vascular Niche ◽

Dynamic Interface ◽

Bone Marrow Vascular Niche ◽

Bidirectional Interactions ◽

Vascular Compartment

Hematopoietic stem cells interact with bone marrow niches, including highly specialized blood vessels. Recent studies have revealed the phenotypic and functional heterogeneity of bone marrow endothelial cells. This has facilitated the analysis of the vascular microenvironment in steady state and malignant hematopoiesis. In this review, we provide an overview of the bone marrow microenvironment, focusing on refined analyses of the marrow vascular compartment performed in mouse studies. We also discuss the emerging role of the vascular niche in “inflamm-aging” and clonal hematopoiesis, and how the endothelial microenvironment influences, supports and interacts with hematopoietic cells in acute myeloid leukemia and myelodysplastic syndromes, as exemplar states of malignant myelopoiesis. Finally, we provide an overview of strategies for modulating these bidirectional interactions to therapeutic effect in myeloid malignancies.

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Mechanotransduction in gastrointestinal smooth muscle cells: Role of mechanosensitive ion channels

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00481.2020 ◽

2021 ◽

Author(s):

Vikram Joshi ◽

Peter R Strege ◽

Gianrico Farrugia ◽

Arthur Beyder

Keyword(s):

Smooth Muscle ◽

Ion Channels ◽

Smooth Muscle Cells ◽

Muscle Cells ◽

Tissue Level ◽

Cytoskeletal Proteins ◽

Cell Junction ◽

Mechanical Stimuli ◽

Junction Molecules

Mechanosensation, the ability to properly sense mechanical stimuli and transduce them into physiologic responses, is an essential determinant of gastrointestinal (GI) function. Abnormalities in this process result in highly prevalent GI functional and motility disorders. In the GI tract, several cell types sense mechanical forces and transduce them into electrical signals, which elicit specific cellular responses. Some mechanosensitive cells like sensory neurons act as specialized mechanosensitive cells that detect forces and transduce signals into tissue-level physiologic reactions. Non-specialized mechanosensitive cells like smooth muscle cells (SMCs) adjust their function in response to forces. Mechanosensitive cells utilize various mechanoreceptors and mechanotransducers. Mechanoreceptors detect and convert force into electrical and biochemical signals, and mechanotransducers amplify and direct mechanoreceptor responses. Mechanoreceptors and mechanotransducers include ion channels, specialized cytoskeletal proteins, cell junction molecules, and G-protein coupled receptors. SMCs are particularly important due to their role as final effectors for motor function. Myogenic reflex-the ability of smooth muscle to contract in response to stretch rapidly-is a critical smooth muscle function. Such rapid mechanotransduction responses rely on mechano-gated and -sensitive ion channels, which alter their ion pores' opening in response to force, allowing fast electrical and Ca2+ responses. Though GI SMCs express a variety of such ion channels, their identities remain unknown. Recent advancements in electrophysiological, genetic, in vivo imaging, and multi-omic technologies broaden our understanding of how SMC mechano-gated and -sensitive ion channels regulate GI functions. This review discusses GI SMC mechanosensitivity's current developments with a particular emphasis on mechano-gated and -sensitive ion channels.

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EFFECTS OF SOME ORGANIC SOLVENTS ON GP lb AND ACTIN-BINDING PROTEIN IN BLOOD PLATELETS

10.1055/s-0038-1643511 ◽

1987 ◽

Author(s):

A M Aakhus ◽

N O Solum ◽

I Hagen

Keyword(s):

Organic Solvents ◽

Von Willebrand Factor ◽

Early Stage ◽

Binding Protein ◽

Blood Platelets ◽

Cytoskeletal Proteins ◽

Actin Binding ◽

Actin Binding Protein ◽

Von Willebrand ◽

Willebrand Factor

Effects on filamentous proteins appear to be a central phenomenon in the neuronal toxic effects of organic solvents. We have therefore compared the effects of some organic solvents (particularly isopropylalcohol, IPA) to the previously observed effects of dibucaine (DBC) on platelet cytoskeletal proteins. Incubation of platelets with 6% IPA at 37° C, like DBC, initiates a degradation of actin-binding protein (ABP) as substrate for a calcium activated protease (CAP), shown by SDS-PAGE. IPA leads to an increase followed by a decrease in bovine von Willebrand factor-induced agglutination. The decrease is accompanied by a release of glycocali-cin from the GP lb α-chain. The process was also studied using CIE of Triton X-100 extracts of platelets against antiserum to glycocalicin. Incubation of platelets with IPA before extraction in the presence of 4.2 mM leupeptin leads to a time-dependent transformation of GP Ib-related immunoprecipitates from that of the slow-migrating peak III complex (probably between ABP and GP lb) to the faster migrating GP Ib-precipitate. Our working hypothesis is that IPA induces an activation of the CAP by mobilizing calcium. This leads to degradation of ABP and liberation of GP lb from the cytoskeleton accompanied by an increased tendency for agglutination. The following decrease is explained by degradation of the glycocalicin part of the GP lb enchain which contains the binding-site for von Willebrand factor. We conclude that IPA has a similar effect on GP lb and ABP as DBC. Preliminary studies with 1% DMSO and 0,005% toluene at 37° C revealed that these organic solvents have some similar effects on platelets as described for IPA. Possibly the described effects are characteristic of certain cells at an early stage in a process ultimately leading to cell lysis.

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Abnormalities of Megakaryocytes in Sl/Sld Mice

Blood ◽

10.1182/blood.v42.6.865.865 ◽

1973 ◽

Vol 42 (6) ◽

pp. 865-871 ◽

Cited By ~ 36

Author(s):

Shirley Ebbe ◽

Elizabeth Phalen ◽

Frederick Stohlman

Keyword(s):

Bone Marrow ◽

Blood Platelets ◽

Normal Concentration

Abstract Megakaryocytopoiesis was evaluated in Sl/Sld mice and their heterozygous and homozygous normal (+/+) littermates. Sl/Sld mice had a normal concentration of blood platelets which were of normal size. Numbers of megakaryocytes in bone marrow and spleen were reduced, but individual megakaryocytes were larger than normal.

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